The present invention relates to dropout compensators, and more particularly to such compensators for use with time spreading codes.
In magnetic tape recording, tape defects or scratches can cause a loss of signal during playback, which is commonly referred to as a dropout. In the case of analog video tape recorders, the occurrence of a dropout results in the loss of a portion of a video scan line, which causes a horizontal streak to appear in the TV picture. A conventional approach to dropout compensation is to replace the portion of the line in error with some average of adjacent scan lines; however, this replacement can result in noticeable distortion in pictures which have very sharp vertical or angular edges. By "vertical edge" is meant that there is an intensity change in the vertical direction. In digital video tape recording, tape dropouts result in the loss of data. If the digital data is recorded on tape in the same sequence as it was obtained from the original analog video signal, then a dropout has the same effect as in an analog recorder, some horizontally adjacent sequence of data in a scan line is lost, and it must be estimated by combining some vertically adjacent data.
It is therefore desirable to selectively use information from one of several directions to reconstruct a signal that has dropped out.